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MORPHOLOGY AND EVOLUTION
spend to the extensor iongus pollicis, arises from the middle third of the antero-medial aspect of the shaft of the fibala and the interosseus membrane. The tendon pa^es under the annular ligament and through the tibrous naviculo-rnetatarsal trochlea to the base of the unguai phalanx of the hallux. Its dorsal expansion is joined by the innermost tendon of the extensor brevis digitoL'um,
The peroneus tertius is absent. This is a human muscle. It combines with the tibialis posticus to steady the foot in walking.
The extensor brevis digitorum is a derivative of the peroneal muscles. In the Chimpanzee it rises from the upper surface of the os calcis, the dorsal calcaneo-cuboid ligament and the external annular ligament. It ends in four slender tendons to the four inner toes, that for the hallux being almost a separate muscle. The innermost tendon goes to the base of the first phalanx, but the others join the long extensor tendons. It is similar to the human muscle in the other Apes.
The peroneus Iongus is as in ilan in the Chimpanzee. Sornmer (491) and Deniker point out that it is as in Man in the Gorilla and Gibbon. And Fick (247) observed the same in the Orang. Hepburn (83) states that it is limited in its insertion to the base of the first metatarsal in the Apes.
The peroneus brevis in the Chimpanzee arises from the outer surface of the shaft of the fibula down to the lateral malleolus, the anterior peroneal septum and the fascia over it. It is inserted into the base of the fifth metatarsal bone, and it gives a slip to the dorsal expansion over the proximal phalanx of the fifth toe. Deniker